Elbow Dislocations

                              Elbow Dislocations  

                                             Dr. KS Dhillon

     

Anatomy and biomechanics of the elbow

There are three joints at the elbow:

• Ulnohumeral joint
• Radiocapitellar joint
• Proximal radioulnar joint

Ulnohumeral joint

The ulnohumeral joint is formed by the articulation between the spool shaped distal medial flare of the humerus called the trochlear and the trochlear notch of the proximal ulna formed by the olecranon and coronoid parts of the ulna. It is a hinge type of joint. Forty percent of the axial load in an extended elbow goes through this joint.

Radiocapitellar joint

The radiocapitellar joint is formed by the the capitellum which is situated on the distal lateral flare of the humerus and the head of the radius. It is a pivot type of joint. Sixty percent of the axial load, with elbow in extension, passes through this joint. The radial head is covered by cartilage for about 240 degrees. The lateral 120 degrees contains no cartilage and this information  useful when internal fixation needs to be carried out.

Proximal radioulnar joint

The proximal/superior radioulnar joint is formed by the head of the radius which articulates with the radial notch of the proximal ulna and the joint shares the capsule of the elbow joint. The two bones are held together by the annular ligament which is attached to the anterior and posterior margins of the radial notch of the ulna. The annular ligament circles round the head and neck of the radius and is devoid of ligamentous attachments which enables the radius to rotate freely inside the annular ligament. It is a pivot type of joint and it allows supination and pronation movements of the forearm.

The elbow joint consists of two types of articulation, and it allows two types of motion. The  ulnohumeral articulation is a hinge joint and it allows flexion and extension, whereas the radiohumeral and proximal radioulnar joint are pivot joints which allows axial rotation. Stability of the elbow joint is provided by the bony articulations and the medial and lateral collateral ligaments.

The primary static stabilizer of the elbow is the ulnohumeral joint (coronoid), medial (ulnar) collateral ligament (MCL) and the lateral collateral ligament complex (LCL).
The ulnohumeral stability is provided its bony counters and the coronoid process. A 50% or more loss of coronoid height results in elbow instability. The MCL is composed of the anterior, posterior and transverse bundles. It arises from the posterior medial epicondyle and inserts on the sublime tubercle of medial coronoid process.

The LCL consists of the radial collateral ligament (RCL), lateral ulnar collateral ligament (LUCL), accessory collateral ligament and the annular ligament. The radial collateral ligament (RCL) extends from the lateral epicondyle to the annular ligament deep to the common extensor tendon. The lateral ulnar collateral ligament (LUCL) extends from the lateral epicondyle to the supinator crest on the ulna. The annular ligament (AL), extends from the posterior to the anterior margins of radial notch on the ulna. It encircles the head of radius and holds it against the radial notch of ulna. The accessory lateral collateral ligament (ALCL) extends from the inferior margin of the annular ligament to the supinator crest.

The secondary static stabilizers are the radiocapitellar joint, the capsule and the attachment of the flexor and extensor tendons (biceps, brachialis, brachioradialis and triceps).
The dynamic stabilizers (muscles crossing the joint) of the elbow includes the anconeus, brachialis, triceps and the biceps.

Classification of elbow dislocation

Dislocations of the elbow can be anatomically classified according to the position of the radius and ulna in relation to the humerus after injury. Based on this there are five types of elbow dislocations :

• Posterior (most common)
• Anterior
• Medial
• Lateral
• Divergent (radius and ulna are dislocated in different directions in relation to humerus)

Complex or simple

Depending on the complexity of the dislocation, the dislocations can be class as simple or complex. Simple dislocations are those where a dislocation occurs without associated fractures and complex dislocations are those where an associated fracture or fractures occur. About 50-60% of  dislocations are simple without associated fractures.

There are three common patterns of complex elbow fracture-dislocations, the trans-olecranon fracture-dislocation, the terrible triad injury, and anteromedial coronoid fractures associated with varus posteromedial instability.

Complex elbow dislocation

Initially evaluation

Clinical examination is carried out to rule out open fractures, neurovascular compromise, and associated injuries. Plain X rays are usually sufficient to diagnose complex elbow fracture-dislocations. A closed reduction is carried out if the elbow is dislocated or the limb is grossly deformed. A CT scan of the elbow is than done to assess the fractures and to guide preoperative planning and treatment.

1.Trans-olecranon fracture-dislocations

Trans-olecranon fracture-dislocations, which result from an axial loading injury, are characterized by the disruption of the ulnohumeral joint with  anterior displacement of the radial head relative to the capitellum. Usually there is a complex, comminuted fracture of the proximal ulna, though a simple or an oblique fracture can also occur [1]. Fractures of the coronoid are also commonly associated with these type of injuries and often the fracture  involves more than 50% of the coronoid height [2]. The radial head can also be fractured [1,3,4]. Coronoid fractures can occur concomitantly as well [5, 7, 8]. The collateral ligaments usually remain intact [1,5].

The fractures are treated by internal fixation via the posterior approach. The coronoid or radial head fracture can approached through the exposure afforded by the olecranon fracture. The olecranon fracture can be stabilized with a plate or a tension band wire. The tension band wire fixation has a higher failure rates [3,4]. Occasional additional medial or lateral incision may be required.

2.Terrible triad injury

In the terrible triad injury the elbow dislocates posterolaterally with an associated fracture of the radial head/neck with a fracture of the coronoid. There is usually an injury to the LCL.
Occasionally these injuries can be treated nonoperatively by close reduction of the elbow and immobilization in 90 degree of flexion for 7-10 days. Nonoperative treatment is carried out when the ulnohumeral and radiocapitellar joints can be concentrically reduced, the radial head fracture is minimally displaced and does not prevent rotation and the coronoid fracture is small. Post reduction the elbow must be sufficiently stable to allow early elbow mobilization.

Surgical treatment is indicated for dislocations with an unstable radial head fracture and a type III coronoid fracture (fractures involving more than 50% of the height).
Stability is restored from inside out and lateral to medial [6,7].
The coronoid is stabilized first with internal fixation or anterior capsular repair, followed by internal fixation or replacement of the radial head. Lateral and medial instability is restored by repair of  LCL and MCL [6,7].

3.Anteromedial coronoid fractures

About 58% (26-82%) of the anteromedial facet of the coronoid is unsupported by the proximal ulnar metaphysis and diaphysis and this makes it vulnerable to injury [8]. Anteromedial coronoid fractures are usually associated with disruption of LCL while the radial head and MCL remain intact [9].

O’Driscoll has classified coronoid fracture into 3 types:

• Fractures of the tip of coronoid
• Anteromedial fractures
• Fractures of the base (body) of the coronoid

The anteromedial fractures are further subdivided into subtype 1 (rim), subtype 2 (rim and tip), and subtype 3 (rim and sublime tubercle) [2].

X rays of the elbow can show these fractures but a CT scan is more useful in the identification of these fractures.

Most of the patients with this type of injury will require surgical fixation
because the elbow lacks stability as a result of the LCL injury and the loss of the medial buttressing effect of coronoid. Subtype 1 fractures can be treated with  LCL repair alone, and subtypes 2 and 3 fractures can be treated with internal fixation using cannulated screws, tension band, or a buttress plate.

Coronoid fractures which are minimally displaced (≤5 mm), or undisplaced with a concentric elbow joint, and a stable range of motion to a minimum of 30° of extension can be treated nonoperatively [10].

Simple elbow dislocation

In patients with simple elbow dislocation a closed reduction is carried out and the elbow is splinted in 90 degrees of flexion for 5-10 days. After about a week mobilization of the elbow is started. An extension block brace is used for 3-4 weeks. Recurrent instability after simple dislocations is rare (<1-2% of dislocations).

Complications of elbow dislocation

Some of the complications of elbow include:

• Failure of internal fixation --Most often seen after repair of radial neck fractures. Poor vascularity can lead to osteonecrosis and nonunion.
• Loss of terminal extension of the elbow--This is a common complication after closed treatment of a simple elbow dislocation. This can be prevent by early, active mobilization of the elbow.
• Varus Posteromedial instability--Injury to the LCL and fracture of the anteromedial facet of the coronoid can lead to varus posteromedial instability. This can be prevented by LCL repair and solid fixation of the anteromedial facet.
• Neurovascular injuries--Open elbow dislocations can be associated (rarely) with brachial artery injuries. Median nerve injuries can be associated with brachial artery injuries. Ulna nerve injuries can result from stretch injuries. 
• Compartment syndrome
• Post traumatic osteoarthritis
• Due to chondral damage and residual instability
• Recurrent instability
• Heterotopic ossification
• Contracture/stiffness
• Post traumatic stiffness --Common after complex dislocation. Early mobilization useful for prevention

Outcome of treatment

Simple dislocations

Generally the outcome of treatment of simple elbow dislocations is good with residual stiffness as a possible complication [11,12]. Recurrent instability can be a concern in patients where early mobilization is opted for whereas in patients where the elbow is immobilized for longer periods, elbow stiffness and contractures may be a problem [13]. Recurrent instability is usually not a problem in patients with simple dislocation. The incidence is low at about 0.3% [14]. There is some low quality evidence to show that the outcome at 2 years follow up in terms of pain and range of movements, favours early mobilization [14].

When the outcome is measure by MEPI score, quick DASH score and weeks off work, functional treatment appears to show significantly better outcomes.
There is no difference between surgical treatment of the collateral ligaments and plaster immobilisation of the elbow joint. Overall, functional treatment with early mobilization appears to provide better movements, less pain, better functional scores, shorter disability and shorter treatment time as compared to plaster immobilisation [14].

The is scarcity of good quality evidence, in literature, on the outcome of treatment of simple dislocations of the elbow.

Complex dislocations

The outcome of treatment of complex dislocations of the elbow have traditionally been poor due to the complexity of injury. Long term complications with such injuries include stiffness, pain, arthritis, and joint instability [15].

Chen et al [16] performed a systematic review of the literature to evaluate the the functional outcome and complications associated with the treatment of terrible triad injuries of the elbow (TTIE).
The review included a total of 16 studies all of which were retrospective in design, involving more than 300 patients. The overall, functional outcomes were satisfactory, but complications (including both those requiring reoperation and those not requiring reoperation) were common. The functional outcomes, as determined by Mayo elbow performance, Broberg-Murray, and/or DASH scores were consistently satisfactory.

Though a high proportion of patients had satisfactory functional outcomes, many patients developed complications, which included ulnar neuropathy, elbow joint stiffness, heterotopic ossification, and arthrosis. About a third of the patients required reoperation due to complications such as instability and/or elbow stiffness.

Rodriguez-Martin et al [17] did a review where they analysed the outcome of treatment of 137 elbow triad injuries in five published studies. The average follow up of the patients was 31 months. The overall outcome was satisfactory with an average flexion arc of 111.4 degrees, and average flexion of 132.5 degrees with forearm rotation of 135.5 degrees. The average Mayo elbow performance score was 85.6 points, and Broberg-Morrey score was 85 points. Complications related to ulnar nerve symptoms, post-traumatic arthritis, elbow stiffness and heterotopic ossification were not uncommon. The symptoms of post traumatic arthritis were mild to moderate in most of the patients who developed joint degeneration. Repeat surgical procedures included capsular release, hardware removal and secondary ulnar nerve transposition [17].

Conclusion

The elbow joint consists of three articulation, the ulnohumeral joint, radiocapitellar joint and the proximal radioulnar joint. It is one of the most inherently stable articulations of the skeleton. Static stability is provided the bony counters, capsule and the ligaments. The muscles crossing the joint provide dynamic stability.

Dislocations can be classified anatomically or based on the complexity of the dislocation. Usually the dislocations are classified as simple or complex. Simple dislocations which are not associated with fractures are easy to treat and the outcome of treatment is generally good with minimal complications.

Treatment of complex dislocations which are associated with fractures is much more difficult. The outcome of treatment of complex dislocations is less predictable and is often associated with more complications.

References

1. Ring D, Jupiter JB, Sanders RW, Mast J, Simpson NS. Transolecranon fracture-dislocation of the elbow. J Orthop Trauma. 1997;11(8):545–50.
2. O’Driscoll SW, Jupiter JB, Cohen MS, Ring D, McKee MD. Difficult elbow fractures: pearls and pitfalls. Instr Course Lect. 2003;52:113–34.
3. Mortazavi SM, Asadollahi S, Tahririan MA. Functional outcome following treatment of transolecranon fracture-dislocation of the elbow. Injury. 2006;37(3):284–8.
4. Mouhsine E, Akiki A, Castagna A, Cikes A, Wettstein M, Borens O, et al. Transolecranon anterior fracture dislocation. J Shoulder Elbow Surg. 2007;16(3):352–7. 
5. Wyrick JD, Dailey SK, Gunzenhaeuser JM, Casstevens EC. Management of complex elbow dislocations: a mechanistic approach. J Am Acad Orthop Surg. 2015;23(5):297–306.
6. Mathew PK, Athwal GS, King GJ. Terrible triad injury of the elbow: current concepts. J Am Acad Orthop Surg. 2009;17(3):137–51.
7. McKee MD, Pugh DM, Wild LM, Schemitsch EH, King GJ. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. Surgical technique. J Bone Joint Surg Am. 2005;87(1):22–32.
8. Doornberg JN, De Jong IM, Lindenhovius AL, Ring D, et al. The anteromedial facet of the coronoid process of the ulna. J Shoulder Elbow Surg. 2007;16(5):667–70.
9. Doornberg JN, Ring DC. Fracture of the anteromedial facet of the coronoid process. J Bone Joint Surg Am. 2006;88(10):2216–24.
10. Chan K, King GJ, Faber KJ. Treatment of complex elbow fracture-dislocations. Curr Rev Musculoskelet Med. 2016;9(2):185-9.
11. Morrey BF, An KN. Articular and ligamentous contributions to the stability of the elbow joint. Am J Sports Med 1983; 11: 315-9.
12. de Haan J, Schep NWL, Zengerink I, van Buijtenen J, Tuinebreijer WE, den Hartog D. Dislocation of the elbow: a retrospective multicentre study of 86 patients. Open Orthop J 2010; 4: 76-9. 
13. Schippinger G, Seibert FJ, Steinböck J, Kucharczyk M. Management of simple elbow dislocations. Does the period of immobilization affect the eventual results? Langenbecks Arch Surg 1999; 384: 294-7.
14. de Haan J, Schep NW, Tuinebreijer WE, Patka P, den Hartog D. Simple elbow dislocations: a systematic review of the literature. Arch Orthop Trauma Surg. 2009;130(2):241-9.
15. Rockwood CA, Green DP (1996) Rockwood and Green's fractures in adults. Philadelphia: Lippincott-Raven.
16. Chen HW. Liu GD and Wu LJ (2014). Complications of treating terrible triad injury of the elbow: a systematic review. PloS one. 2014, 9(5), e97476. doi:10.1371/journal.pone.0097476.
17. Rodriguez-Martin J, Pretell-Mazzini J, Andres-Esteban EM, Larrainzar-Garijo R. Outcomes after terrible triads of the elbow treated with the current surgical protocols. A review. Int Orthop. 2010;35(6):851-60.